Airplanes and sailboats

[BobW]

Kinetic energy released = ZERO

because that's you 2 docks over hugging your masthead and screaming for help, cussing Etienne (ATN) and yelling at the rest of us as we gather to laugh and discuss your plight as we enjoy our beers. We sent the guy with the glass of chardonnay back to his Oyster, because this is MAN'S work.Many suggestions are put forward (one wag even put a can of beer at the base of your mast, in an adaptation of the 'get the cat out of the tree' solution), but the one we go with is to move the boat out of the next slip and tip your boat jussssstttttt far enough so when you let go you'll do a cannonball into the water.And since you've just proven - conclusively - that you're actually moving at 870.2 knots....... well...... I suggest you time your jump pretty carefully. ;DAfter you splash down.... and we have another beer.... we'll have another beer and calculate your terminal velocity. Looks like you just about scrubbed off that .2 knots! One more beer and we'll notice you thrashing about in the water (weighed down by the tool belt you were wearing, no doubt) and call the chardonnay guy to rescue you.Cheers,Bobs/v X SAIL R 8proud owner of a new, un-used, ATN Climber ;D

 

[tom]

Moody I think you are wrong

If the windows in the plane are shut the air inside is part of the planes mass. The fly in the air or on the dash is also part of the plane's mass. To fly the fly must expend energy downwards equal to it's mass X G. This moves the air downward and the downward air hits the floor of the plane pushing downward. Since the weight of air inside the plane is the same as the weight outside it is ignored(neutral bouyancy) but the weight of the fly is greater than the weight of the air that it displaces. Actually many planes are pressurised and heated so the weight of the air can be a factor probably many times the weight of a fly. Now to the bigger question.. If the plane is burning 50#s of fuel/hour will it eventually be weightless??? Back to the wheel. Circular motion is best described as angular velocity and all points of the wheel rotate through the same degrees/minute. Assuming no slippage the outer circumference of the tire is traveling at the same speed as the car. The angular velocity and linear velocity are related by 2 pi r = c . 5280/c = revolutions/mile X mph = revolutions/hour x 60 = rpm's x 360 = degrees/minute . It's been a long time since I taught math and physics so you might want to check my numbers.

 

[Ross]

I think that the question of the weight

of the fly in an enclosed air space can be resolved emperically. Place the fly in a jar and put the lid on. Place the jar on a sensitive scale and observe the total weight with the fly resting. When the fly takes flite again observe the weight.

 

[NautiDuck]

Everyone go work on their boats!

Brian D, you should be drawn and quatered and then walk the plank for posting this. Puting out a question like that is like throwing chum into a shark tank. Entertaining but bloody.Everyone else, go work on your boats or read a nautical book or peruse the new WM catalog or ogle pictures of Stef. You are all suffering from some sort of land-based-dimensia that has you arguing over the potential weight of a fly in suspension.NOBODY IN THEIR RIGHT MIND CARES ABOUT THE FRIGGIN' FLY!!!I feel better now.;-)

 

[Persy]

"fly in suspension" uh oh.........

take cover...

 

[Ross]

RandyK, You left out hanged! and

keel hauled and floged throgh the fleet.

 

[Dan Johnson]

I wanna know...

how the tarmac was made to move in the original question....LOL!!!

 

[Ross]

Don, Ya know those movable walkways at

the airport? Well they just scaled them up a little. NO? How about an earthquake? NO? What did you say they were smoking?

 

[Brian D]

Wow...

My bad.

 

[Stu Jackson]

So, you're on a scale with a brick in your hand

and you look at the scale and it says 180 lbs. The brick weighs 5 lbs. You throw the brick up in the air. While it's up, you look at the scale and it says _____________? Maybe easier than figuring out a fly in a plane.Yup, been a looooong winter.......

 

[Ross]

Stu , Not the same. Must be a closed system

brick must be pulverized to 5 micron particle size so that it will remain in suspension. Or you can take a wasp nest in there with you and weigh the system while they are cold and on the nest. then wait for them to warm up and take flight.

 

[tom]

The brick has inertia

When you toss the brick you accellerate it and the weight on the scale temporarily increases this is because you must exert a force on the brick greater than gravity so that the brick moves upward. Since the brick isn't flying it's exerting no weight on the scale once it is no longer being accelerated. Now the same thing with the fly. If the fly jumps up into the air it is suspended by inertia and exerts no weight on the plane. I guess you get into weight versus mass. Weight is the mass being accellerated by the force of gravity. In steady state flight the fly is exerting downward force on the air equal to it's weight. The difference in force is apparent to people up north. They can walk on thin ice but if they try to jump up and down they might break through. If we ignore drag the brick wil hit stu on the head with the same amount of energy as he imparted to the brick when he tossed it upward. But it will hurt more because he accelrated the brick though several feet but it will stop almost instantly when it hits his head.

 

[sailortonyb Allied Mis]

The boat will not make headway

This is the basis for the theory of relativity. All is relative to everthing around it.If you are in your car driving at 10 miles per hour, and there is a car next to you doing the same thing, then relative to eachother, you are not moving. relative to someone standing on the street corner, you are moving at 10mph. Now if someone is going in the opposite direction at 10mph, then you are passing eachother at 20mph as a relative speed to eachother.In an airplane, a given amount of airflow must take place for a wing to fly. Again this is relative in the sense that the airflow will make the wing fly whether the plane is on the ground with an 80mph wind on its nose or with no wind on the ground but the plane is moving at 80mph. Either way will work.Sailors call it 'apparent' wind. If you were on a train moving at 60mph and sitting down, then you are traveling at60mph to the observer at stationary point. Now if you were to walk forward in the train at 3 mph, then to the same observer, you are now passing him at 63 mph and are traveling faster than the train itself, yet you are only going 3 mph relative to someone else sitting down on the train. Until of course, you break your nose hitting the front door and can no longer move forward. Once you fall backward, then you are now moving slower than the train to a person sitting on a park bench watching all this silliness. Tony B

 

[tom]

Wow Tonyb now that you have classical physics

Tonyb you have a good grasp or Newtonian physics so please explain advanced physics. I just can't wrap my mind around the comcept of light speed. Supposedly nothing can go faster than the speed of light. If you take an atom and accellerate it to near the speed of light and it radioactively decomposes the light it emits won't be any faster. If Captain Kirk is zooming around on his starship at light speed and passes a Vulcan ship at light speed going the other way they pass each other at light speed??? Must have something to do with time slowing down near light speed. But this makes no intuitive sense to me. It has been confirmed experiemntally that nothing travels faster than light regardless of the frame of reference.

 

[sailortonyb Allied Mis]

Not even light can....

From what i remember, not even light can travel at the speed of light, go figure. I think the Star Trek theory used the idea that of you can create a warped space field, then get this field to approach the speed of light, and this being a large field, you can move forward inside the field and thus be traveling faster than the field relative to the ousdie world. Keep in mind, the days i learned physics, they didnt have drug screening, and a good joint helped in staying philosophical. If you get 'high' enough, everything seems reasonable, LOL. Been missing a lot of this forum lately. My new 'blue water rehab' has really bad communications systems. Can not even access internet at most times. TomH....now that I have established myself in Tx, I am getting moved up your way for work out of Mobile Bay. Tony B

 

[henkmeuzelaar]

Stinkpotters no headway; (most) sailors sternway!

When sailing on any other point of sail than DDW a "boat speed" equalling 10 knot through the water will be slightly less than 10 knot in the direction the bow is pointing because of side-slip. So, when "heading into a 10 knot current" most sailing vessels will actually make some negative headway (aka sternway) when measured over the ground. Boat speed through the water will not be affected, of course.Have funFlying Dutchman

 

[henkmeuzelaar]

If we jump straight up inside an airplane

that is flying with constant velocity along a straight and level trajectory (with fully enclosed cabin and zero interior airflow velocity) will we land in the same spot we stood or will the spot where we land be offset towards the tail of the plane?If we can answer that question (e.g. by trying it out next time we fly) I am confident we will also find the correct answers to the fly-in-the-plane questions.Warning: I don't know a whole lot about aerodynamics and don't think I have found the "correct" answer myself yet.Have funFlying Dutchman

 

[Stu Jackson]

My head hurts

but not from this thread, it's been lotsa fun. Tom, I kept forgetting to look up and,dagnabbit, you're right the damn brick hit me right on the head! My weight, while I was looking down, was 175 (after the acceleration thingy calmed down), and when the brick fell into my hand after bouncing off my head it went back up to 180.I missed the fly with the brick though.

 

[Stu Jackson]

One question to small plane fliers

If a small plane needs say 40 mph to rotate, does the fact that these planes are literally tied down when they are parked mean they could start flying if the wind exceeded 40 mph from dead ahead? What are the dynamics of flights in those conditions, or should I just Google it like I tell everyone else to do about boats?

 

[Ross]

Stu, I had an old flight line sargent tell me of a

time when a light obsevation plane came in during a storm and they manhandled it on to the ground. The pilot couldn't get his airspeed down to stop flying without being blown backwards.